The present invention is directed to a control for an appliance and more particularly to an electronic control for a compactor having a split-phase induction drive motor.
In a conventional refuse compactor, a ram is driven into a refuse disposal compartment to compact trash disposed therein and continues advancing until the motor stalls. The ram is subsequently driven out of the refuse disposal compartment. Various drive mechanisms for refuse compactors are disclosed in U.S. Pat. No. 3,353,478 to Stephen Hawkin; U.S. Pat. No. 3,732,805 to Jerry W. Moon; U.S. Pat. No. 3,772,987 to Charles R. Difley; U.S. Pat. No. 3,839,954 to Joseph F. Burgeois; U.S. Pat. No. 3,921,515 to William A. Eckerle; U.S. Pat. No. 4,007,678 to John K. C. Gustavson, et. al.; U.S. Pat. No. 4,188,877 to Aman U. Khan; and U.S. Pat. No. 4,565,125 to Aman U. Khan.
Various mechanical and electronic controls have been designed for regulating the operation of the drive mechanisms of a trash compactor. For example, Einar O. Engebretsen shows a compactor cycle control in U.S. Pat. No. 3,962,964 wherein a dwell period is provided at the end of the compaction cycle.
U.S. Pat. No. 3,855,919, Richard W. Potter shows a control system for a compacting apparatus including signal lamps for showing the direction of movement of the ram. The apparatus includes a time delay circuit for automatically shutting down the compactor when any of the operational cycles thereof continues beyond a predetermined time limit.
In U.S. Pat. No. 3,398,433 of Charles J. Borum, a trash compactor with a clock timer control is disclosed for providing an extended delay period after a compacting stroke. The clock is provided to permit the automatic extended compaction at a period of time during the day when the compactor is unlikely to be in use for a substantial length of time. The control operates the ram independently of any manual initiation of the apparatus to effect the compacting stroke at the predetermined time and to cause the stopping of the ram for the delay period during that independently initiated compaction stroke. In U.S. Pat. No. 3,543,676 of Gordon H. Brown, another refuse compactor is shown having control circuitry for regulating the operation of the compactor automatically.
Michael J. Bottas et al, in U.S. Pat. No. 3,613,560, show a refuse compactor including a control circuit which permits operation of the ram only when the drawer is substantially in the compacting position. The control circuit includes a tilt switch which is arranged in the circuit to permit reverse withdrawal movement of the ram by depression of a manually operable pushbutton.
Jerome F. Stratman et al, in U.S. Pat. No. 3,821,927 show a refuse compactor control system having a lower limit switch connected in parallel with a centrifugal switch.
In U.S. Pat. No. 3,831,513 of Philip Tashman, a portable solid waste compactor is shown having a compacting ram which has a stroke varying with the reaction force of the waste material being compacted therein. An interlock associated with the ram prevents operation of the compactor upon removal of the container in which the refuse is compacted. A guard gate is automatically closed across the refuse chute opening upon downward compacting movement of the ram to prevent injury to the operator's hand. If the guard gate is prevented from closing by an obstruction, a switch causes immediate reversal of the ram to its uppermost position.
In U.S. Pat. No. 4,062,282, Samuel Jacob Miller et al show a refuse compactor having a tilt switch for terminating operation of the compacting ram in the event of a preselected tilt movement of the receptacle during the compacting operation. Means are provided for preventing movement of the receptacle sufficient to open the receptacle safety switch during the compacting operation thereby preventing discontinuation of energization of the ram motor during the compaction cycle which could immobilize the compactor apparatus in midcycle.
While these prior art control patents teach that it is desirable to monitor performance of a compactor to determine, for example, when compaction is complete or when the bag is full, the prior art uses multiple sensors, typically mechanical sensors, to monitor the operation. Furthermore, the maximum torque applied is limited to the main winding breakdown torque.
A more generic control system for various appliances having an AC induction drive motor, including examples of an automatic washing machine, a dryer, an air conditioner, a refrigerator, and a dishwasher, is shown in my U.S. Pat. No. 4,481,786, assigned to the assignee of the present invention. That control system employs a ferrite core sensor having a primary winding that is formed of two turns of the drive motor's run winding, the sensor having a single turn secondary winding that forms a sense winding coupled to a motor phase monitoring circuit. The sense winding provides a signal representing a polarity change in the run winding current. The current polarity change signal is used by the motor phase monitoring circuit to provide a voltage compensated motor phase angle pulse to a microcomputer for the appliance to control various operations of the appliance. More particularly, a digital representation of the motor phase angle pulse is used by the microcomputer to monitor the starting of the drive motor by detecting a characteristic decrease in the motor phase representation. The motor phase angle representation is further used by the microcomputer of an automatic washing machine to determine the agitator torque which is in turn used by the microcomputer to automatically control the water level of the washing machine. An average motor torque number is also determined from the motor phase angle representation wherein the average motor torque number is used to provide an end of drain control for the washing machine.
While my prior patent application suggests that the control may be used to control any AC induction motor controlling any appliance, including a split phase induction motor controlling a trash compactor, the applicability or desirability of such a control to the specific needs of a compactor was neither addressed nor considered. The present invention is directed to a control utilizing some of the teachings of my aforementioned U.S. patent to a refuse compactor but applying a novel circuit and novel logic to detect the onset of stalling as the ram compacts the refuse and using that information to control the operation of a compactor in a novel way.